The role of lattice mismatch in the deposition of CdTe thin films

Cadmium telluride (CdTe) is the most well-established II–VI compound largely due to its use as a photonic material. Existing applications, as well as those under consideration, are demanding increasingly stringent control of the material properties. The deposition of high-quality thin films is of utmost importance to such applications. In this regard, we present a report detailing the role of lattice mismatch in determining the film quality. Thin films were deposited on a wide variety of substrate materials using the pulsed laser deposition (PLD) technique. Common to all substrates was the strong tendency toward the preferential alignment of CdTe’s (111) planes parallel to the substrate’s surface. X-ray diffraction analysis, however, revealed that the crystalline quality varied dramatically depending upon the substrate used with the best results yielding a single-crystal film. This tendency also manifested itself in the surface morphology with higher structural perfection yielding smoother surfaces. The film quality showed a strong correlation with lattice mismatch. Texture analysis using the [111] pole figure confirmed that improvements in the lattice mismatch led to a higher degree of in-plane alignment of the (111) grains.